In 1912, while working for Parke-Davis pharmaceutical, chemist Wilbur Scoville devised a test to measure the piquancy (that's "hotness") of various chili peppers.

This one is the Naga Jolokia pepper [wiki], the hottest pepper in the world at 850,000 to 1 million units on the Scoville scale. In comparison Jalapeño is just 5,000 to 15,000 units and habanero is about 100,000 to 500,000 units in the Scoville scale.

See the list of the Hottest Chili Peppers and Hot Sauces in the World - Thanks Mike Stanton!

to anyone who eats a naga and does not virtually die from its effects is not human. these will hurt you bad. and there is a bonus: after taking a tiny taste: about an hour later if you burp you get to experience all that pain again. Second bonus: trying to go to the bathroom later on without screaming out loud.